Either way the architect is just going to say; 'I knew nothing about woody's designs, I simply worked up the clients design instructions'.
If I pursue it, then perhaps just the threat of some action, and reporting him to his club, may be enough to give him the wobblies.
If that fails, then from some reading of past cases, it does seem that if he merely saw my sketch, or if the client described my design to him, then that could be enough. It is knowledge of the concept of the design which matters.
I am still really annoyed about this, as his client was a right pain - calling me numerous times for various advice and information from design, to build costs, contract advice for the builders and then other advice about other defects around their house! I spent considerable time advising them, and then some other bloke comes along and gets the job
A claim may even work if I include the client and the Architect - that could help me if the client told the Architect that she wanted him to use my design. Then they can argue between them